ActiveMQ延迟和定时投递

AMQ的延迟和定时投递用起来非常的简单，可根据产品的需要在消息生产时添加必要的属性，即可达到目的。前提是已经为Broker添加了“调度支持”。

来自官方的说明：

http://activemq.apache.org/delay-and-schedule-message-delivery.html

ActiveMQ from version 5.4 has an optional persistent scheduler built into the ActiveMQ message broker. It is enabled by setting the broker schedulerSupport attribute to true in the xml configuration.
An ActiveMQ client can take advantage of a delayed delivery by using the following message properties:

Property name	type	description
AMQ_SCHEDULED_DELAY	long	The time in milliseconds that a message will wait before being scheduled to be delivered by the broker
AMQ_SCHEDULED_PERIOD	long	The time in milliseconds to wait after the start time to wait before scheduling the message again
AMQ_SCHEDULED_REPEAT	int	The number of times to repeat scheduling a message for delivery
AMQ_SCHEDULED_CRON	String	Use a Cron entry to set the schedule

For the connivence of Java JMS clients - there's an interface with the property names used for scheduling at org.apache.activemq.ScheduledMessage.

For example, to have a message scheduled for delivery in 60 seconds - you would need to set the AMQ_SCHEDULED_DELAY

property:

MessageProducer producer = session.createProducer(destination);
TextMessage message = session.createTextMessage("test msg");
long time = 60 * 1000 ;
message.setLongProperty(ScheduledMessage.AMQ_SCHEDULED_DELAY, time);
producer.send(message);

You can set a message to wait with an initial delay, and the repeat delivery 10 times, waiting 10 seconds between each re-delivery:

MessageProducer producer = session.createProducer(destination);
TextMessage message = session.createTextMessage("test msg");
long delay = 30 * 1000 ;
long period = 10 * 1000 ;
int repeat = 9 ;
message.setLongProperty(ScheduledMessage.AMQ_SCHEDULED_DELAY, delay);
message.setLongProperty(ScheduledMessage.AMQ_SCHEDULED_PERIOD, period);
message.setIntProperty(ScheduledMessage.AMQ_SCHEDULED_REPEAT, repeat);
producer.send(message);

You can also use CRON to schedule a message, for example, if you want a message scheduled to be delivered every hour, you would need to set the CRON entry to be - 0 * * * * - e.g.

MessageProducer producer = session.createProducer(destination);
TextMessage message = session.createTextMessage("test msg");
message.setStringProperty(ScheduledMessage.AMQ_SCHEDULED_CRON, " 0 * * * *");
producer.send(message);

CRON scheduling takes priority over using message delay - however, if a repeat and period is set with a CRON entry, the ActiveMQ scheduler will schedule delivery of the message for every time the CRON entry fires. Easier to explain with an example. Supposing that you want a message to be delivered 10 times, with a one second delay between each message - and you wanted this to happen every hour - you'd do this:

MessageProducer producer = session.createProducer(destination);
TextMessage message = session.createTextMessage("test msg");
message.setStringProperty(ScheduledMessage.AMQ_SCHEDULED_CRON, " 0 * * * *");
message.setLongProperty(ScheduledMessage.AMQ_SCHEDULED_DELAY, 1000 );
message.setLongProperty(ScheduledMessage.AMQ_SCHEDULED_PERIOD, 1000 );
message.setIntProperty(ScheduledMessage.AMQ_SCHEDULED_REPEAT, 9 );

producer.send(message)